I enquired about this when quoted for a 60,000 mile service. It took some arguing the case before the dealer agreed that I might be right.
My book, for a 2000Y GS300SE says 100,000 miles before needing a belt change, but, I underatand that Lexus moved the service spec to 9000 mile intervals for later models and specified 63000 miles for a belt change.
This puts £300 on top of the usula charges.
Did Lexus lower the interval because of problems or did later models have a larger wear and tear rate?